Hydraulic tappet



June 21, 1960 P. F. BERGMANN HYDRAULIC TAPPET Filed Jan. 14, 1959 4.. Iwa 4, v

INVENTOR PAUL F. BERGMANN ATTORNEY .provides a seal between thereservoir limited HYDRAULIC TAPPET This invention relates to tappets ingeneral, and more particularly to hydraulic tappets.

Hydraulic tappets are used in automotive and other engines as slackadjusters for the engine valve lifting means. When an engine is justbeing started, the parts on an engine valve lifter train are contractedand consequently of less length than under normal engine operatingconditions. As an engine warms up and the engine temperatures rise, thevalve train parts expand and increase in length. Tappets areself-adjusting means which are interposed in the engine valve operatingtrain to compensate for the change which takes place.

The most commonly known and used type of hydraulic tappet is one inwhich a variable capacity fluid chamber space is used to transmit thevalve lifting force. This may be accomplished by having a plunger memberdisposed within a blind end passage to form such a :fluid chamber space.The volume of the chamber space is decreased to compensate for valvetrain growth by bleeding fluid off through the clearance space betweenthe plunger and the blind end passage forming member.

The bleed-ing off of hydraulic fluid through the clearance space betweenthe plunger and the plunger receiving member is commonly known asleakdown. Leakdown control is entirely dependent upon holding closetolerances in the plunger and cylinder members of the tappet to obtain aminimal clearance space therebetween. Quite obviously, it is expensiveto machine the parts to the required close tolerances, to inspect andsort the parts, and to later assemble them. Over or under sizedclearance spaces will result in an ineffective tappet.

It is an object of this invention to provide a hydraulic tappet in whichthese close tolerances and minimal clearances are not required to be soclosely maintained.

It is an object of this invention to disclose valve means which may beused to control the fluid bleed off from the pressure chamber space inhydraulic tappets. Accordingly, the close tolerances and minimalclearance spaces are no longer required to be so carefully maintained.There is also less stringency in the inspection and sorting of thetappets and no appreciable problem in the assembly of the tappet parts.

It is also an object of this invention to disclose a simple andrelatively inexpensive form of relief valve means for the pressurechamber space and one which may be incorporated within presently knownhydraulic tappets. No appreciably expensive tooling changes arenecessary. The valve means is simply interposed between the plunger andpush rod seat members.

Another object of this invention is to disclose a highly suitablepressure chamber valve means for use in hydraulic tappets. The reliefvalve hereinafter described inlet to the tappet and the pressure chamberspace. control ,valve between the reservoir inlet and reservoir chamberspace. 7

Still another object of this invention is to disclose a relativelysimple and inexpensive pressure chamber valve means, in and of itself.The valving member is 'a 'coned or dished annular ring having its outeredge formed as It also serves asa v stem Patented June 21, 196i) asealing means and its inner edge notched for allowing fluid flow to thereservoir chamber under certain operating conditions.

Another problem prevalent in conventionally known tappets, particularlyat high engine speeds, is a condition known as tappet pump-u Thecommonly known form of hydraulic tappet provides for continuous oralmost continuous communication between the hydraulic fluid supplysource and the reservoir chamber of the tappet. At high engine speedsthis free communication of fluid to the reservoir chamber, the inherentresiliency in the valve train parts, engine valve spring fluctuations,etc., set up false requirements for tappet adjustment which cause apremature and generally incorrect exchange of fluid between thereservoir and pressure chambers.

In addition to the objects of this invention aforementioned, it is anobject to disclose a tappet in which all adjustment of the effectivelength of the tappet occurs while the tappet is on the base circle ofthe actuating cam. This avoids the necessity for communication betweenthe fluid supply source and the reservoir chamber during the tappetstroke. Accordingly the reservoir feed passage may be closed during thetappet stroke to avoid any false response attributable thereto.

Another object of this invent-ion, with respect to avoiding tappetpump-up, is to provide a novel means of reservoir communication and onewhich may be readily shut otf during tappet operation.

Still another object of this invention, with respect to tappet pump-upproblems, is to disclose an anti-surge means for use withina tappet tocompensate for resiliency in the valve train parts and engine valvespring fluctuations, which normally create false conditions for tappetadjustment.

A further object of this invention, in the same vein, is to discloseanti-surge means incorporated within another operable tappet part.Accordingly no extra tappet parts are required and the material andassembly costs of the tappet are not increased in providing such anaddi-' tional feature.

These and other objects and advantages in the practice of this inventionwill be more apparent in the illustration and description of a workingembodiment of the invention, as hereinafter set forth.

In the drawings:

Fig. l is a cross sectional plan view of a hydraulic tappet includingthe features of this invention.

Fig. 2 is an enlarged fragmentary section of the tappet shown by Fig. 1illustrating the relief valve in one of its operating positions.

Fig. 3 is an enlarged fragmentary section of the tappet shown by .Fig."1 illustrating the relief valve in another of its operating positions.a i

.Fig. 4 is an enlarged fragmentary section of the tappet of Fig. 1showing the plunger and valve means, per 'se.

.Fig. 5 is an enlarged top plan view of the valve member itself.

The hydraulic tappet shown in the drawings includes a cylindrical memberclosed at its lower end and having a passage formed therein to receive aplunger member. The plunger member forms a pressure chamber space withthe blind end of the cylinder body "and is hollow to form a reservoirchamber space. A check valve is provided at the "end of the plungermember hetween the reservoir and. pressure chamber spaces. :Acompression spring is disposed Within the pressure chamber space to biasthe plunger away from the :"closedend of the cylinder body.

A push. rod seat, for the push rod member of th'e engine valve train, isdisposed within the open end of tlie cylinder body. It is disposed overthe plunger member of the tappet is not immediately apparent.

understood in the following detailed description of structure andoperation.

; Thehydraulic tappet includes a cylindrical tappet body member 20having its lower end 21 closed. The

within a guide passage 11 in an engine valve block 12 (shown inphantom).

and] is formed to close the reservoir chamber space thereof.

The relief valve of this invention is provided between the push rod seatand plunger members. The push rod ,seat member includes an undercutannular groove-to sup- 'ply hydraulic fluid to the reservoir chamberspace through the relief valve. The outer periphery of the relief valveforms a seal between the annular pressure chamber space,

between the plunger and cylinder bodies, and the reservoir supply grooveof the push rod seat member. 7

During the operation of the tappet the operating cam raises the cylinderbody member and the fluid in the pressure chamber space, beingincompressible, transmits such force to the plunger member. The plungermember acts against the relief valve, closing the reservoir feeding side.At that moment the push rod member seeks to move the plunger memberlower within the cylinder body, causing an increase in the pressurewithin the pressure chamber spaces, and results in the relief valveraising to permit a bleed off of fluid and the lowering of the plungermember.

The specific operation of the relief valve will be better cylinder bodymember 20 is mounted for reciprocation The outer surface of the cylinderbodymember 20 is formed to include a wide annular groove 22 near itsupper end. The groove 22 cooperates with a reservoir feed galley 13 inthe engine block '12:- A passage 23 is formed through the tappet bodymember20, within the annular groove 22, for communi- ..cation with thecylindrical chamber space 24 thereof.

An engine valve operating cam 14 is mounted under the-blind end 21 ofthe tappet body member 20. The eccentric end 15 of the cam is intendedtolift the tappet body member within the engine block guide passage .11.An engine valve operating push rod member 16 v; is received within theopen end of the cylindrical chamber space 24 and is engaged with certainparts of the tappet 10 to be described. The engine valve spring (notshown) acts through the-push rod member 16 to keep the tappet engaged onthe cam 14 at all times.

Within the cylindrical passage 24 of the tappet body =member 20 there isdisposed the tappet plunger member 30. The plunger member 30 forms apressure chamber ;-space 25 with the blind end of the tappet body memberThe end of the plunger member is necked down as at 31 and includes apassage 32 therethrough which is closed by a check valve 40. Thecylinder body member 20 is undercut at 26, around the lower end of theplunger member 30, and is formed to provide a bottoming shoulder 27 forthe plunger member. A check valve cage 41 is fitted on the end of theplunger member 30 within the pressure chamber space 25; -=The cage 41includes a flange 42 upon which'is received .the upper end of a coiledcompression spring .28. The compression spring 28 is disposel within thepressure chamber space 25 and bears against the blind end thereof. Thevalve cage 41 may be press fitted on the necked end 31 of the plunger 30or may be held engaged thereto by the spring 28.

- The check valve is disposed within the valve cage 41. The check valve40 includes a light coiled compression spring 42 seated on the valvecage andholding a valve plate 43 against the end of the passage 32 whichupper end of the chamber space 24, of the tappet body 4 is formedthrough the plunger member 30. The valve cage 41 includes an end opening44 and side openings 45 to allow fluid flow therethrough.

The tappet plunger member 30 is formed to include a reservoir chamberspace 33. The passage 32 is in open communication'with the reservoir 33.The upper end of the plunger member 30 is formed to include an annulargroove 34 about its outer periphery and to provide a valve seat face 35at the terminal end thereof.

Between the plunger member 30 and the cylinder body- 20 is an annularclearance space 29. This clearance space is in the order of .004. Ascompared to the .0002 clearance space previously required to bemaintained between these parts, for leakdown controlled tappets, suchspace is in eifect part of the pressure chamber space 25. The annularspace 29' about the upper end of the plunger .rnember 30 is similarly tobe considered part of the pressure chamber space 25 since it is in opencommunication therewith through the clearance space 29.

A push rod seat member 50 is disposed within the upper end of the blindend passage 24 of the tappet body member. The push rod seat member 50includes a wide annular groove 51 within its outer periphery andextending to its lower end. A'valve seat face 52 is provided on itslower terminal end. The valve seat face 52 is annular and includes aboss 53 with a coned side wall 54 centrally thereof. The boss 53 extendswithin the reservoir space 33 of the plunger 30 when the push rod seat50 is seated thereover.

. The upper end of the push rod seat 50 is formed to include a sphericalseat 55 for the ball headed end 56 of the push rod member 16. l

Between the valve seat face 52 of the push rod seat 50 and the valveseat face 35 of the plunger 30 is disposed the valve member 60. Thevalve member 60 is a dished .and preferably thin metallic annular disk,as shown in Figs. 4 and 5, in a substantially free state. The outerperipheral edge of the valve disk 60 is formed downwardly and out, as at61. T he inner peripheral edge 62 forms an opening which is smaller thanthe boss 53 on the end of the push rod seat member 50. Notches 63 areprovided in the inner edge 62 of the valve plate at circumferentiallyspaced intervals.

As shown by Fig. 4, the outer peripheral edge 61 of theivalve membernormally bears against the side wall 'of' the cylinder passage 24. Whenthe push rod seat member 50 and the plunger member 30 have the valve '60"seated therebetween, as in Fig. 2, the outer edge 61 is held againstthe cylinder wall with a resilient forc'e resulting from forciblystraightening out the dished disk. Further, the inner peripheral edge 62of the valvemember is bent down by the coned wall 54 of the push rodseat boss 53 extending beyond the plunger valve seat face 53. This cutsoh. and closes communication between the reservoir feed groove 51 andthe reservoir space 33 via the notches 63.

The different dispositions of the valve member 60 will be furtherdescribed in the discussion of tappet operation which follows.

A snap ring groove 18 is formed internally within the member, and a snapring 19 is received therein to keep the parts mentioned assembled asdescribed.

OPERATION v The tappet 10 is shown in Fig. l with the engine valveclosed. The push rod member 16 is in its lower extended position. Thevalve member 60 holds the push rod seat member 50 and plunger member 30spaced apart. The resilient strength of the inner periphery 62 of thevalve plate 60 is sufliciently greater than the plunger return spring 28to hold the push rod seat and plunger menibers separated. However, it isof less strength than the engine valve spring, to be assured that theengine valve is closed. The return spring 28 is of suflicient strengthtenses E to hold the valve seat 35 closed on the valve plate and theouter peripheral edge under compression against the cylinder space wall.

When the engine is started, hydraulic fluid at engine operating pressureis supplied to the reservoir chamber space 33. The fluid flow is throughthe galley passage 13, groove 22, and passage 23 into the cylinder body.The flow continues through the annular groove 51 about the push rod seat50, under the end face 52 thereof, and through the valve plate notches63 into the reservoir.

As the valve operating cam 14 rotates and brings its eccentric end 15under the blind end 21 of the cylinder body member 20, the tappet bodymember begins its rise. The hydraulic fluid within the chamber spaces25, 29 and 29' is trapped by the valve 60 seated on the plunger end 35.The fluid, being incompressible, transmits the lift force to the plungermember 30 and raises it with the cylinder body member 2i). The plunger30 lifts the valve plate 60 towards the push rod seat 50 and causes theinner periphery 62 thereof to fold down and allow the valve to seat onthe push rod seat 52. This closes the reservoir feed passage. Theplunger member 30 acts through the valve plate 60 and against the pushrod seat 50 to raise the push rod member 16 and initiate the opening ofthe engine valve (not shown).

The resistance ofiered by the engine valve spring (not shown), toallowing the engine valve to be opened, is an increasingly greaterresistant force as the engine valve spring is compressed. The increasingresistant force to tappet movement (as part of the valve actuatingtrain) is counterbalanced by a greater fluid pressure force built upwithin the pressure chamber space 25. During the rise of the tappet andthe increase in this fluid pressure condition there is an equalizationof fluid pressure within the pressure chamber connected spaces 29 and29'. The larger clearance in the annular space 29 enables a more readyresponse to a change in the fluid pressure condition of the pressurechamber space 25 than in conventionally known leakdown type tappets.

As the crest of the eccentric end 15 of the valve operating cam 14passes under the end of the tappet body 20, the tappet begins itsdescent. There is no appreciable change in the relationship of thetappet parts. As the engine valve operating spring expands in closingthe engine valve, and its resistant force depreciates, the fluidpressure condition in the pressure chamber space 25 also drops oif. Anygrowth in the eflective length of the valve train parts is not yetapparent in effecting any change in the operation of the tappet 10.

During the descent of the tappet to the base circle of the cam 14, itwill be appreciated that the pressure condition in the annular chamberspace 29' is falling oil as is the pressure condition in the pressurechamber 25.

As the tappet body member 20 approaches the base circle of the cam 14,any growth in the valve train parts will become apparent. The push rodmember 16 returns to a lower relative position than it previouslyoccupied. The push rod seat member 50 also assumes a lower relativeposition. The valve member 60, through the resiliency of its innerperiphery 62 acting against the push rod seat member 60, urges theplunger 30 and the cylinder body 20 toward the base circle of the cam14.

Because of the lower relative disposition of the push rod seat 50 thevalve member 60 is not aflforded suflicient space to open as before.Consequently the resiliency of the valve plate 60 acts against theplunger 30, creating an increased fluid pressure condition in thepressure chamber spaces 25, 29 and 29. This pressure, in the annularspace 29, lifts the valve 60 ofi the valve seat to bleed suflicientfluid from the pressure chamber spaces to allow the plunger to assume alower relative position Within the cylinder body, as it is required todo.

When the plunger member 30 has assumed its properly 3 readjustedposition, within the cylinder body 20, the reservoir chamber space 33 isopen to the annular feed groove 51 through the notches 63 in the valve60.

Should the fluid pressure condition in the pressure chamber spaces fallbelow that of the reservoir chamber 33, the check valve 40 will open topermit an equalization of fluid pressure therebetween. This will occuronly while the tappet is on the base circle of the cam 14 since thereservoir chamber 33 is normally closed during the tappet stroke.

The resilient character of the valve member 60 enables it to serve as ananti=surge means and to prevent false pressure conditions in thereservoir space 33 which might otherwise open valve 40 and create atappet pump-up problem. The spring strength of the valve plate member 66is greater than that of the plunger return spring 28. Thus, any variancein the engine valve spring resistance, on the push rod seat '50, due toengine valve spring fluctuations, will be countered by the valve member60 rather than the plunger return spring 28. Otherwise, the plunger 30would adjust its axial position upward in the cylinder body 20, thevalve 40 would open to allow fluid to flow into the pressure chamberspaces, and a pump up problem would exist. The resilient character ofvalve 60, through its inner peripheral edge 62, prevents prematureadjustment of the plunger by exerting a restraining force on its upperend which compensates for the resistance lost in the fluctuation of theengine valve spring, or whatever cause, and which is greater than theplunger return spring force at its lower end.

After the engine valve train parts have expanded to full length, undernormal engine operating conditions, there is no necessity for the valve60 to lift ofl the plunger seat 35.

The valve member 60 serves H to prevent the leakage of hydraulic fluidpast the plunger 30 during the operation of the engine valve. Tappetadjustment takes place upon the return of the tappet to the base circleof the operating cam 14. This is a more stable time for ad justment thanat the peak of the cam as with conventional leakdown type tappets. V

The member 60 also serves as a spring element to effect the separationof the push rod seat member 50 and the plunger 30 to both controltheleakdown of hydraulic fluid from the pressure chamber spaces, andtheentrance of fluid into the reservoir space. In all instances the valvemember 60 serves as a seal separating the reservoir feed passage 51 fromthe pressure chamber space 29.

While a preferred embodiment of this invention has been described, itwill be understood that other modifications and improvements may be madethereto. Such of these modifications and improvements as incorporate theprinciples of this invention are to be considered as included in thehereinafter appended claims unless these claims by their languageexpressly state otherwise.

I claim: 7

1. A hydraulic tappet, comprising; a tappet body member having reservoirand pressure chamber defining parts relatively reciprocal therein, acheck valve member disposed between one of said parts and said bodymember for passing fluid from. the reservoir chamber to the pressurechamber defined by said parts, and a resilient valve member disposedbetween said chamber defining parts for opening and closing saidreservoir chamber to a fluid supply source and for closing and ventingsaid pressure chamber to said reservoir chamber.

2. A hydraulic tappet, comprising; a tappet body member having reservoirand pressure chamber defining parts relatively reciprocal therein, acheck valve member disposed between one of said parts and said bodymember for passing fluid from the reservoir chamber to the pressurechamber defined by said parts, and a resilient valve member disposedbetween said chamber defining parts for opening and closing saidreservoir chamber to a fluid supply source and for closing and ventingsaid pressure chamber to said reservoir chamber, said valve member-having a valve seat face provided on one side thereof for engaging oneof said chamber defining parts and closing one of the chambers definedthereby and another -valve seat face provided on the other side thereoffor engaging the other of said chamber defining parts and closingtheother of the chambers defined thereby.

a fluid supply source and for closing and venting said pressure chamberto said reservoir chamber, said valve member having a valve seat faceprovided on one side thereof for engaging one of said chamber definingparts and-closing one of the chambers defined thereby and another valveseat face provided on the other side thereof for engaging the other ofsaid chamber defining parts and closing the other of the chambersdefined thereby, and said valve member further having its outerperipheral edge formed and disposed to provide a seal between saidchamber definding parts precluding the exchange of fluid 1 I betweensaid pressure chamber and the supply source for said reservoir chamber.

' 4. A hydraulic tappet, comprising; a tappet body member havingreservoir and pressure chamber defining parts relatively reciprocaltherein, a check valve member disposed between one of said parts andsaid body member for passing fluid from the reservoir chamber to thepressure chamber defined by said parts, and a resilient valve memberdisposed between said chamber defining parts for opening and closingsaid reservoir chamber to a fluid supply source and for closing andventing said pressure chamber to said reservoir chamber, said valvemember comprising a dished annular-ringfor holding said chamber definingparts apart under certain operating conditions of said tappet to providefluid flow access therethrough from a reservoir supply source to saidreservoir, said'dished ring yielding to external forces urging saidchamber defining parts together for receiving said parts in chambersealing engagement on opposite sides thereof,

and upon therelief of said external forces said sealing ring beingresponsive to an excessive pressure condition Within said' pressurechamber to lift and provide fluid flow'access from, said pressurechamber to said reservoir.

5. A hydraulic tappet, comprising; a tappet body mem ber havingreservoir and pressure chamber defining parts relatively reciprocaltherein, a check valve member dis- -posed between one of said partsandsaid body member for passing fluid from the reservoir chamber to thepressure chamber defined by said parts, and a resilient valve memberdisposed between said chamber defining parts for opening and closingsaid reservoir chamber to a fluid supply source and for closing andventing said pressure chamber to said reservoir chamber, saidvalvernember comprising a dished annular ring having its outer peripheryreceived in sealing engagement with said tappet 'body member and itsinner periphery engageable with oneof said chamber definding parts, saidinner periphery including notches permitting fluid flow therethroughbetweena fluid supply source and said reservoir chamber,

and the other of said chamber defining parts being received in valveseat engagement with said valve member :between said outer and innerperipheries.

6. In a hydraulic tappet including a tappet body member having a blindend passage formed therein, a plunger member received in said passageand forming a pressure chamber space with the blind end thereof, a pushrod seat member received in said passage and forming a reservoir chamberspace with said plunger member, means provided; within saidtappet bodymember for. biasing member, and control means provided between saidplunger and push rod seat members for the opening and closing of saidreservoir with respect to said fluid supply means -and with respect tosaid pressure chamber space: said control means comprising; a dishedannular sealing ring having fluid flow accesses formed within the innerperipheral edge thereof, said sealing ring having suflicient resiliencewhen said tappet is stationary to hold said plunger and push rod seatmembers separated against the opposition of said biasing means for theflow of fluid from said fluid supply means through said accesses to saidreservoir and insufiicient resilience to resist the seating" of saidring in sealing engagement on the end of said plunger member for closingsaid pressure chamber.

7. In a hydraulic tappet comprising a tappet body rnernb'erhaving ablind end passage formed therein and relatively reciprocal plunger andpush rod seat members disposed within said passage, said plunger beingformed to provide a reservoir chamber space, said push rod seat memberbeing disposed relative to said plunger for closing said reservoirspace, and control means between said plunger and push rod seat membersfor controlling fluid flow to said reservoir therebetween, said controlmeans comprising; a dished annular sealing ring having reservoir feedingaccesses provided in the inner peripheral edge thereof and a sealingflange provided about the outer peripheral edge thereof, said sealingring having valve seating faces provided on opposite side faces thereofbe suflicient to resist the compression of said ring between saidplunger and push rod seat members for closing said accesses when saidtappet body member is in motion.

8. In a hydraulic tappet including a tappet body memher having a blindend passage formed therein, a plunger member received in said passageand forming a pressure chamber space with the blind end thereof, a pushrod seat member received in said passage and forming a reservoir chamberspace with said plunger member, means provided within said tappet bodymember for biasing said plunger and push rod seat members in engagement,check valve means provided between said reservoir and pressure chamberspaces for the uni-directional flow of fluid from said reservoir to saidpressure chamber space, fluid supply means provided through said tappetbody member, and control means provided between said plunger and pushrod seat members for the opening and closing of said reservoir withrespect to said fluid supply means and with respect to said pressurechamber space:

said control means comprising; a dished annular sealing ring havingreservoir feeding accesses provided in the inner peripheral edge thereofand a sealing flange provided about the outer peripheral edge thereof,said sealing ring having valve seating faces provided on opposite sidefaces thereof between said peripheral edges, and said sealing ringhaving such resilience as is suificient to hold said plunger and pushrod seat members separated when said tappet body member is separated, toallow fluid flow through the accesses in the inner peripheral edgethereof, and is insufiicient to resist the compression of said ringbetween said plunger and push rod seat members for References Cited inthe file of this patent UNITED STATES PATENTS Humphreys July 22, 1958Skinner Mar. 12, 1957 Re. 24,506 g,7 s4,707

